1. Field of the Invention
The present invention relates to an apparatus and method for diverting the surface flow of a body of water.
2. Description of the Relevant Art
Annually, about 645 million tons of oil are transported on United States waterways in areas where currents routinely exceed one knot. In addition, thousands of facilities located on the banks of fast-current waterways store millions of gallons of oil. Additionally, thousands of oil pipelines traverse fast-water rivers, and bays, also posing oil spill threats. Between 1992 and 1998, about fifty-eight percent of all oil spilled in the U.S. was spilled in fast-current waterways. This figure represents about 4.5 million gallons of oil spilled in swift flowing rivers, harbors, bays and coastal areas where conventional boom and skimmers may be ineffective.
Containment and removal of oil and other floating contaminants spilled in inland rivers and coastal tidal regions where currents exceed one knot may be very difficult because many skimmers and conventional booming methods may not be effective in fast currents. When skimmers or booms are used in currents that exceed about one knot, contaminants may be entrained in the water flow and follow the water path under the boom or skimmer. Containment and removal of floating contaminants in currents exceeding one knot may be accomplished using specialized equipment and tactics; however, properly trained response personnel may be essential for ultimate success. Tactics to contain and remove contaminants in currents over one knot may include: skimming the contaminants off of the surface as they go by a recovery device; slowing the current down without causing entrainment of the contaminants, then skimming the contaminants off of the surface; or redirecting the contaminant with a diversion device to an area where the current is slower and effecting the recovery there. Benefit may also be derived by diverting contaminants away from sensitive areas and by concentrating them for recover or other remediation methods.
Fast water may create large drag forces on vessels and equipment making them difficult to anchor and maneuver, and may often cause equipment failure (e.g., submergence, planing, or breakage). Maneuvering vessels and equipment in fast water may be dangerous to both personnel and equipment. Fast water may also accelerate many spill processes necessitating quicker and more efficient responses compared to stagnant water or slow moving current conditions. Timely response efforts may be required in order to minimize environmental damage, economic losses and associated cleanup costs
A Boom Vane was developed to deploy a deflection boom from shore without the need of a boat or mid channel anchor. The device includes a series of paravanes fixed to a frame with a surface float rudder, one main tension line, a bridle and a control line. The device uses hydrodynamic forces to pull the Boom Vane and an attached deflection boom out into a current. The Boom Vane is positioned in the water at an equilibrium point where hydrodynamic lift is balanced by the main tension line and the boom drag. The rudder controlled by a line allows retrieval of the system.
Another spill clean up system is a floating deflector system. The floating deflector system includes a series of large (approximately 16.4 feet high by 34 feet long) independent parallel foils spaced about 34 feet apart using cables or lines. The deflectors were designed to divert a potential oil spill from upstream oil processing facilities from a fast moving portion of a river, to a slow moving portion of the river. The deflector system was designed to be deployed from a fixed location on the shore. Each deflector was designed to have a submergence depth between ⅓ and xc2xd the mean water depth.
An embodiment of a flow-diverter disclosed herein may be composed of two foil assemblies. At least one of the foil assemblies may include a buoyant member (or xe2x80x9chullxe2x80x9d). At least one of the foil assemblies may include a hydrofoil (or xe2x80x9cfoilxe2x80x9d) that extends at least partially into the water. In certain embodiments, both foil assemblies may include a buoyant member and a foil. A foil may extend from the bottom, side, top, or an end of the hull and extend into the water. The foil assemblies may be connected in a xe2x80x9ccatamaranxe2x80x9d configuration by one or more cross members above the water. Additionally, none, one or more cross members may be connected to the bottom of the foils. At least one of the cross members, usually above the water, may be rigid to keep the foil assemblies separated. The foils may float approximately vertically in the water in a catamaran configuration. The cross members may be free to pivot about a vertical axis at their attachment to the hulls and foils. Thus, each foil assembly of a catamaran may be free to move relative to the other foil assembly but remain parallel to each other. The catamaran hulls may be linked with neighboring catamaran hull pairs by cables, lines, or rigid links attached to the ends of the cross members to form a string of diverter catamarans. These catamaran connection lines/cables/links may generally be the same length as the cross members. The most inboard foil assembly of a catamaran or string of catamarans may be connected to shore, a support vessel, or a fixed structure in the water with one or more control lines. Each control line may be bridled to the upper and lower ends of the cross members to prevent the catamaran from rolling due to the lateral loads on the foil assemblies and to distribute loads evenly between the hulls and foils. The bridle arms may be adjustable using short sections of chain, shackles or other such means at the bridle apex. In a current or when pulled through a body of water, the angle of attack of the catamaran or string of catamarans may be controlled by adjusting the length of a first control line relative to a second control line. The foils and hulls may thus form a cascade that generates a lateral force with a magnitude dependant upon the foil and hull shape and the angle of attack of the foil assemblies to the oncoming flow. This lateral force (or xe2x80x9cliftxe2x80x9d) may move the catamaran or string of catamarans out into the current where they may reach a steady state position when lift and drag of the system, balanced against control line tension are equal. The foil assemblies may create a lateral force and may present a physical barrier that deflects the surface flow at an angle close to the cord lines of the foils and lateral to the onset flow. This diversion current may thus transport floating contaminants in a direction toward the mooring control line side downstream, lateral to the onset flow. The catamaran or catamarans may also be quickly retrieved back to a deployment point by either reversing the angle of attack, or increasing the angle of attack until the foil is stalled.
An advantage of embodiments disclosed herein may be that due to their small size, they may be deployable from a vessel or from shore, by one or two people. Additionally, small size may allow a catamaran, or catamarans to be transported easily and deployed quickly.
Another advantage may be that the catamaran configuration may provide substantial roll stability, while allowing catamarans in a string of catamarans to adjust to waves or other surface flow effects individually. This roll stability may prevent planing or submergence of the foils due to uneven control line forces, uneven bridle line forces, or environmental forces (e.g., wind and current) on the catamaran(s).
Another advantage of the embodiments disclosed herein may be that a number of catamarans may be effectively strung together to form a string of catamarans. This expandability may increase the flexibility and sweep effectiveness of the system.
Yet another advantage may be that the catamaran configuration, which is collapsible, may facilitate deployment, retrieval, storage and transportation of the system.